It is desirable to have lids on waste containers to contain unpleasant sights and odors, and to protect against contamination from objects therein. Various waste containers with hand-operated lids have been developed, but suffer from inconvenience in use and risk of contamination when touched. Foot-operated designs minimize contamination risk, but are also often inconvenient or bothersome to use. Users of both hand and foot operated waste containers may be occupied with multiple tasks, or be situated in an inconvenient position, and not have a free hand or foot to operate the container lid.
Automatic cans of two general types have been developed. One type uses a proximity detector (e.g., pressure-sensitive mat or photoelectric detector) to sense the presence of a user in the vicinity of the container and actuate motor-driven door(s) to open. Doors generally close after a predetermined time period of non-detection. This type of automatic can is readily prone to false alarms from passing objects or persons.
The second type of automatic trash container has a physical ‘bay’, which objects must enter prior to passing through the automatic door of the container. The bay has one or more infrared beam emitters and detectors. Objects in the bay reflect beams of the infrared light zone and cause the motor-actuated door to open. The walls of the bay shield against detection of objects outside the bay.
Elimination of false alarms is improved with this type, but ‘false negatives’, or the non-detection of objects in the bay, is possible if objects are situated outside the zone.
Additionally, the requirement for an inner bay compromises the automatic waste container's ability to contain contaminating objects and noxious emissions to the can's shielded interior. The inner periphery of the bay, which may become contaminated, is exposed. It is difficult to avoid this condition when a shielded photoelectric detection zone is created in front of an opening. The zone must be offset some distance from the door by an exposed physical structure so the door can be opened before incoming objects make contact. For the user to pause while the door opens is inconvenient, so the comfortable zone offset distance is significant.
What is required is an automatic waste container that creates a non-physical detection zone, with a precisely controlled configuration to minimize false triggerings. For a can with an upward-facing opening, the detection zone should be a continuous, vertical ‘curtain’ matching the profile of the opening periphery, so only objects crossing the virtual, vertically-extended boundary of the opening activate the can. This configuration reduces the detection zone boundary to a logical minimum, thereby substantially decreasing unintentional triggerings. It is also desirable for the height of the detection zone to be adjustable by the user in order to avoid false triggerings by the presence of nearby structure, objects or zones of activity situated in the area above the can.
Diffuse light curtains, with continuous sensing ability, are known in various applications. They generally utilize diverging or scanning beam, infrared emitters and photodetectors to create continuous zones of detection by sensing reflected emissions from intruding objects. Emissions may be pulsed at a fixed frequency, and electronic and logic circuitry so configured, so as to filter out all received radiation not at the emitter frequency. This curtails false triggerings, as well as variations in detector sensitivity caused by fluctuations in ambient lighting conditions.
Light curtains have been used in industry to create safety zones around operating machinery that initiate immediate shutdown signals, or other safety protocols, when the zones are transgressed. Other applications include detection systems for sensing moving objects on a conveyor belt or breaks in fabric in textile manufacturing machines. Light curtain detection systems have also been employed for monitoring passing vehicles on traffic thoroughfares. Intruder alarm systems, used in various security applications, have also utilized light curtains for defining detection zones. Another application is the use of light curtains to control automatic, pedestrian doors when prescribed zones around the doors are entered.
Light curtains have been developed that utilize both diverging and non-diverging, or collimated, beampaths. It is conceivable that technology developed for other light curtain applications may be applied towards developing the light curtain configuration required for an improved automatic waste container. However, known light curtain technology has several drawbacks when considered for this application.
Even where light curtains are collimated to create planar detection zones, no provision is described in the prior art for creating a single, continuous light curtain circumscribing a prescribed area.
Multiple, planar light curtains may be combined to create a polygonal boundary, but this can only approximate curved, non-polygonal perimeters. Additionally, the cost and complexity of combining multiple light curtains created by prior art technology to enclose a defined area is prohibitive when considered for the current goal of creating an inexpensive, automatic waste container.
Thus it is desirable to create a low-cost, robust, reliable detection system suitable for use in connection with automatically-actuated containers, such as waste containers.